Effect of electrolyte composition on zinc hydroxide precipitation by lime

The effect of effluent composition on the efficiency of the hydroxide precipitation of Zn2+ modelling lime (CaO) as a precipitant has been predicted using the solubility domain approach and experimentally validated. Solubility domains were based on the phases that were found to be solubility limiting for systems representing potential effluent chemical composition limits. All such phases were found to resemble their mineralized counterparts with a lower degree of structural order. The generated solubility domains generally encompassed the experimentally observed solubilities, thus providing effluent treatment quality assurance ranges for the hydroxide precipitation process. The presence of calcite (CaCO3) and gypsum (CaSO4.2H(2)O) as secondary precipitates had little effect on the observed residual zinc solubilities. Validation of the solubility domain approach using real industrial wastewater was accomplished. (C) 1997 Elsevier Science Ltd.